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Abstract(s)
A refrigeração, numa perspetiva doméstica ou industrial, assume um papel preponderante na sociedade. Possuindo como principal objetivo a minimização dos processos de formação de organismos bacteriais, despontou nas civilizações antigas como um processo de armazenamento de gelo natural no inverno, para utilização posterior no verão. Hoje em dia, grande parte dos processos de refrigeração são dirigidos, principalmente, ao armazenamento de produtos alimentares e ao arrefecimento de espaços fechados.
Desde a projeção do primeiro dispositivo de refrigeração industrial, no século XVIII, o método de remoção de calor do ar ambiente por intermédio da evaporação de um fluido ainda se demonstra hoje em dia um processo de melhoria contínua. A partir dos anos 60, verificou-se uma incidência mais forte, na tentativa da melhoria do processo de refrigeração quanto aos níveis de consumo energético.
Aliando a importância e a utilização global de processos de refrigeração e criogenia, à necessidade de redução do consumo energético, a investigação sobre métodos de aperfeiçoamento de sistemas de refrigeração surge como uma temática meritória no ramo da engenharia.
Uma das limitações dos mecanismos de refrigeração usuais, que tem levado ao desenvolvimento de mais investigações no ramo, é a formação de gelo na superfície externa dos evaporadores constituintes do ciclo de refrigeração. Uma vez que grande parte dos dispositivos operam segundo um ciclo de compressão mecânica de vapor, é garantido que nestes exista um componente evaporador.
A presente dissertação foi desenvolvida para determinar de que forma o processo de deposição de gelo nos evaporadores afeta o rendimento térmico do circuito de refrigeração, no seu todo, quando o escoamento de ar é sujeito a diferentes níveis de temperatura, humidade relativa e caudal volúmico. É feita posteriormente a proposta de uma solução para a atenuação da formação de gelo em superfícies metálicas do componente evaporador. Os resultados obtidos garantem a redução da resistência térmica, parâmetro este originado pelo surgimento de gelo, quando o circuito de refrigeração opera com base na estrutura desenvolvida.
Refrigeration, in a domestic or industrial point of view, takes a very important role in society. Once its main objective is the minimization of the formation of bacterial entities, it blunted in the old civilizations as a process of natural ice storage in the winter, for subsequent use in the summer. Nowadays, a big portion of the refrigeration processes are taken into account in the food and drinks storage, and also in the cooling of closed spaces. Since the projection of the first ever industrial refrigeration device, in the eighteenth century, the method of heat removal from the surrounding air through the evaporation of a fluid, still demonstrates itself as being a process of continuous improving. Since the 1960’s, a stronger incidence was verified, regarding the attempt of improving the process of refrigeration in terms of the energetic consumption levels. Bonding the importance and the global use of refrigeration and cryogenic processes, to the necessity of energetic consumption reduction, the development of methods to perfect refrigeration systems appears as a relevant thematic in the engineering field. One of the restrictions of the usual refrigeration mechanisms, which has led to the development of more essays in this subject, is the icing verified in the external surface of the evaporators, as a part of the refrigeration cycle. Once that great part of the devices operate according to a mechanic vapor compression cycle, the presence of an evaporator component is guaranteed. The present dissertation was developed to determine in which way the process of ice deposition in the evaporator affects the thermal efficiency of the refrigeration circuit, when the air draining is subject to different levels of temperature, relative humidity and volumetric flow rate. Then, it proposes a solution for the attenuation of the frozen particles deposition, in the metallic surfaces of the evaporator. The obtained results guarantee the reduction of the thermal resistance, originated by the ice sprouting, when the refrigeration circuit operates according to the developed structure.
Refrigeration, in a domestic or industrial point of view, takes a very important role in society. Once its main objective is the minimization of the formation of bacterial entities, it blunted in the old civilizations as a process of natural ice storage in the winter, for subsequent use in the summer. Nowadays, a big portion of the refrigeration processes are taken into account in the food and drinks storage, and also in the cooling of closed spaces. Since the projection of the first ever industrial refrigeration device, in the eighteenth century, the method of heat removal from the surrounding air through the evaporation of a fluid, still demonstrates itself as being a process of continuous improving. Since the 1960’s, a stronger incidence was verified, regarding the attempt of improving the process of refrigeration in terms of the energetic consumption levels. Bonding the importance and the global use of refrigeration and cryogenic processes, to the necessity of energetic consumption reduction, the development of methods to perfect refrigeration systems appears as a relevant thematic in the engineering field. One of the restrictions of the usual refrigeration mechanisms, which has led to the development of more essays in this subject, is the icing verified in the external surface of the evaporators, as a part of the refrigeration cycle. Once that great part of the devices operate according to a mechanic vapor compression cycle, the presence of an evaporator component is guaranteed. The present dissertation was developed to determine in which way the process of ice deposition in the evaporator affects the thermal efficiency of the refrigeration circuit, when the air draining is subject to different levels of temperature, relative humidity and volumetric flow rate. Then, it proposes a solution for the attenuation of the frozen particles deposition, in the metallic surfaces of the evaporator. The obtained results guarantee the reduction of the thermal resistance, originated by the ice sprouting, when the refrigeration circuit operates according to the developed structure.
Description
Keywords
Atenuação. Evaporador Formação de Gelo Refrigeração Resistência Térmica